Impacts on Conventional Generators

Impacts of Renewable Electricity Generation on Efficiency and Emissions of Conventional Generators

With increasing penetration of wind and solar generation, conventional fossil-fired power plants may be required to adjust their output level, start up, or shut down more frequently to accommodate the variability and uncertainty of these technologies. These operational changes can negatively impact plant efficiency and emissions. NREL's analyses are focused on understanding and quantifying the emissions and costs associated with these operational changes.

While the emissions impacts of generator cycling and part-loading can be significant (e.g., combined cycle generators), these impacts are modest compared to the overall benefits of replacing fossil-fuel generation with variable renewable generation.

Highlights of Recent Studies

Western Wind and Solar Integration Study - Phase 2

This study investigated the cost and emissions associated with the increased cycling and ramping of conventional fossil-fueled generation due to higher levels of solar and wind generation. Key findings include:

Part-load emissions impacts increase the NOX benefits of wind by approximately 8%, while startups and ramping emission impacts reduce the NOx benefits of wind by approximately 4% (based on re-analysis of the Western Wind and Solar Integration Study (WWSIS) generation profiles).